The need for requesting emergency services is common in communication systems. Commonly known, standard emergency numbers are helpful to eliminate caller confusion during emergency situations. When a user dials the standard emergency number (e.g., 911 in the United States), the telephone switch receiving the emergency call makes a decision as to where to route that call. In prior-art systems, the routing decision is based on the location of the fixed instrument from which the call is made. One problem with this system is that a user in an unfamiliar country may not know the proper standard emergency telephone number for that country.
Various countries throughout the world use different numbers to obtain emergency call services. As mobile subscribers roam between these countries, the subscriber units must generate the appropriate emergency number to the serving network, and identify the call attempt as an emergency call.
Some countries, such as Japan, employ more than one emergency number for emergency services. There are three emergency codes used in Japan. These are (110) for Police services, (118) for Fire services and (119) for Marine services. Cellular systems which support user mobility use a technique called Cell-Based Routing to route a call identified as an emergency call to the closest emergency center based on the cell in which the user is currently located. The subscriber unit must therefore recognize the dialed code as an emergency code to signal the serving network that this call is in the emergency category. In large cellular systems, such as satellite systems, the dialed emergency code is only valid for a particular area, and may need to be translated to another emergency number prior to being transmitted to the serving network. For example, the (110) code which is valid in Japan must be translated to a (911) code in the United States.
What are needed are methods and systems for determining emergency call routing in a satellite-based cellular communication system. What are further needed are methods and systems for determining emergency call routing in which a user may use different emergency numbers when located anywhere in the world.